We propose to develop in vitro systems for studying the disposition of xenobiotics. More specifically, we will evaluate the feasibility of developing improved systems for the study of excretory transport into the bile. Two independent systems will be developed in parallel: (1) new methods for the efficient isolation of enriched bile canalicular membrane vesicles (BCMV) from human donor tissue and (2) heterologous expression of cDNAs encoding bile canalicular membrane transporters. Kinetic and inhibition studies will be conducted with known substrates in order to characterize the transport properties of tissue-derived vesicles and the heterologously-expressed transporter. The eventual goal is to develop a comprehensive system for the study of human excretory transport. PROPOSED COMMERCIAL APPLICATION Active transporter preparations for the prediction of xenobiotic disposition in humans. These systems are complementary to commercially available xenobiotic metabolizing systems.